Check processing systems are well )mown in the art. These require intense illumination means as workers know, especially with "electronic-imaging" where images of the two sides of a check are taken, stores and retrieved--as opposed to physically handling checks to process them. Many difficulties and disadvantages of prebent systems relate to how well the checks are illuminated. If the documents are not properly illuminated and imaged, the result is apt to be errors in reconciling and balancing check transactions and in reporting to customers (e.g. monthly statement).
Workers recognize that electronically-stored data ("electronic images") of documents can be processed much quicker, more reliably and less subject to error (than the documents themselves). But to do this, one must first capture an accurate image and convert it into electronic computer (EDP) signals. The EDP image-signals can then be manipulated (e.g. be recorded, be reproduced for visual review, be sorted and distributed, etc.) much more rapidly, easily and more reliably than physical documents.
Systems for "electronic imagelift" will conventionally contemplate using a video camera by which an operator views the actual document as desired. Based on what he sees, the operator can then electronically enter document-data into a computer system; e.g., such things as check-amount, account number and other data necessary for processing document transactions. Such physical viewing is labor-intensive, is subject to error (e.g. from operator fatigue) and is substantially slower than an automated image-capture, -manipulation arrangement.
Workers are beginning to think of using imaging technology as a way of improving document processing, as disclosed, for example, in U.S. Pat. Nos. 4,510,619; 4,205,780; 4,264,808; 4,672,186 and 5,098,713. Generally, imaging involves optically scanning documents to produce electronic images that are processed electronically and stored on high capacity storage media (such as magnetic disc drives and/or optical memory) for later retrieval and display. It is apparent that document imaging can provide an opportunity to reduce document handling since the electronic images can be used in place of the actual documents.
It would be somewhat conventional to contemplate document processing and associated "image capture" using conventional video cameras, with conventional light sources, one to illuminate each side of a document, plus various lenses to focus light onto the document. Successive document-images ("image slices") can be reflected from the document, front and rear, into respective video cameras, which can convert the optical image into electronic signals; which can then be converted by appropriate circuitry into digital form. But the foregoing would have serious disadvantages; e.g. it would require conventional light sources and conventional camera systems--something expensive to provide and cumbersome to coordinate.
U.S. Pat. No. 5,098,713 addresses such disadvantages; e.g. teaching use of a single, high-intensity, well-cooled light source (cf. high-output xenon bulb, requiring substantially less power than a conventional two-lamp system); and mounting the light source and associated optical components on a base (e.g. for ready access, for maintenance and for better thermal isolation).
The present invention modifies the illumination portion of such arrangements for "modest systems", i.e. relatively smaller, slower, simpler, less expensive systems; e.g. for use in a table-top, low speed, proof-type machine, such as for front-office and teller-station applications. Such a machine can typically be used for immediate encoding and endorsing of checks and other similar financial instruments, one at a time, on demand and in small volumes. For such applications, low cost and small size are important. Our preferred modest, camera for this is adapted to image documents at a relatively modest flow rate, e.g. 30 documents per minute, at a document speed of the order of 15 inches per second.
Such a machine can form a pivotal part of a "return item processing" system, intended to allow the semi-automated processing of documents which are unreadable by conventional high speed automated equipment (e.g. at 1800 documents per minute), or which are selected by the customer for manual processing for a variety of reasons. Such items may include (but are not limited to) documents which are unencoded when presented to the customer, damaged in transit, or selected for special processing due to their value. For these reasons, such a machine should have both Imaging and OCR (Optical Character Recognition) capabilities.
In view of the modest document-f low rate, relatively less document illumination is required for imaging. To our surprise, we have found that fluorescent lamps in an appropriate configuration, can provide sufficient light.
In a preferred embodiment, our machine is specified with one or two separate (but identical) cameras: a front camera, which is always present; and an optional rear camera which may be replaced by a blanking plate. In this way, a customer who desires to image only the front of the document may be accommodated at lower cost.
Details
One important objective in designing a camera for such imaging is to provide illumination of highly uniform and constant intensity, both from top-to-bottom (and side-to-side, of beam) of the document and also across track-depth (i.e. of the track within which the document is constrained and driven). Highly-desirable are low-cost, simple and readily-obtained parts; thus, fluorescent lamps might be a desirable source of illumination if their intensity/uniformity were adequate. But this would likely be viewed by artisans as highly unlikely.
Initial Concept
FIG. 3A represents (plan view) the kind of camera we first contemplated, with documents advanced along a track DT past an illumination aperture SL, with lamps L.sub.1, L.sub.2 illuminating the respective Front/Rear imaging-sites (IS, IS'; offset from one another); the document images to be sent to sensor means along some imaging path OP. (FIG. 3B represents a modification of the FIG. 3A arrangement and is detailed below.)
Our first thought was to see if relatively conventional fluorescent lamps were adequate for illuminating such an imaging station (e.g. in camera like FIG. 3). FIGS. 6A, 6B represent this, where we used a pair of such lamps to symmetrically bracket the imaging site and send the reflected document-image back between the lamps. Lamps T'.sub.1, T'.sub.2 will be understood as a pair of relatively conventional fluorescent tube lamps disposed to symmetrically bracket intermediate imaging-path 1P (in phantom, FIG. 6A), with a shield serving to define an illumination-slit SSL (like SL in FIG. 3). To avoid the "dark-ends" of each tube [reduced intensity, nonuniformity] we tried masking-off the two "dark-ends" of each tube T'.sub.1, T'.sub.2 from the passing documents with slit SSL(see document Doc in FIG. 6A, the leading end of a check thrust along track DT on base plate BP; thus the height of slit SSL is set to correspond with maximum expected document-height.
Workers will recognize how convenient it is to so illuminate a document-site symmetrically from both sides and send the document image back between the lamps (to be captured by CCPD or like camera means). In fact, we were surprised that such an arrangement could give adequate illumination.
However, such an array of lamps seemed excessively "tall", so we conceived bending both lamp ends to reduce their height (e.g. see FIG. 6C, a modification of FIG. 6B, where the tubes are so bent; only T".sub.2 shown). Of course, such a right-angle bending keeps the dark-ends, obscured so they don't affect document-illumination; however, one countervailing disadvantage is that machine width may be increased (i.e. in direction of bent ends). But this latter disadvantage may be ameliorated by a reentrant, or 180.degree., bending of tube ends as in FIGS. 4A, 4B--especially where the tube tubes are replaced by a single over-long tube which is bent 180.degree. to yield the two illuminating segments (as in FIGS. 1-4; detailed elsewhere).
Problems with Fluorescent Lamps
A common problem with illumination from fluorescent lamps is the "dark zone" of reduced intensity at either end of the lamp tube (in the region of the cathodes and/or the filaments by which the tubes are emergized). This "dark zone", is an unavoidable by-product of lamp operation and typically extends about 1" to 2" along either end of the tube, where intensity is much lower than that for the rest of the tube (i.e. along its intermediate "medial" segment).
But, we have found, to our surprise, that this "medial" segment, for a miniature-type fluorescent lamp (e.g. approximately 7 mm in diameter) could be adequate in intensity, wavelength spectrum and uniformity for the "modest" imaging applications previously described. It was quite surprising that a mere fluorescent lamp could be made adequate.
To further avoid the problems of reduced intensity and poor uniformity associated with the "dark zones", we tried not only bending the tube ends reentrantly, but also placing both ends "behind" the central (uniform-light) tube segment, opposite the document site. In effect, this "hides" the "dark zones" from the document which thus "sees" only the medial segment (see FIG. 4A, referring to medial segment CS and "dark zones" DE)--while "competing" the array, minimizing it's height and depth.
At first, this seemed impractical as possibly restricting the fluorescent discharge and degrading lamp illumination. But we found that if a fluorescent tube is so bent such that the bend-radius doesn't exceed tube-radius, the tube will operate satisfactorily; i.e. under such conditions, it's discharge will follow the elongate tube-axis as effectively as if the tube were straight (unbent). if the bend is more severe, illumination (discharge) is compromised.
A more conventional approach might be to only mask-off, the "dark zones", and leave the tube straight, as in FIGS. 6A, 6B above described. But this is impractical here, for the tubes we contemplate, of the tube-length taken up by the "dark zones" would make the camera (housing) undesirably "tall". And bending the ends 90.degree., and shielding them (e.g. as in FIG. 6C, described above) undesirably extends machine depth and height.
Another approach might be to partially opacify (filter) the central tube segment so that its intensity more closely matched that of the ends. But this seemed impractical because it extends machine height (as above) and because the intensity of the ends is, itself, not uniform; also it varies with age and other factors; further the length of a "dark zone" tends to increase unpredictably as the tube ages (typically after several thousand hours of operation).
An object hereof is to address at least some of the foregoing problems and to provide at least some of the mentioned, and other, advantages.